Ceph: An Introduction to the Distributed Storage System

Nowadays, the need for scalable, flexible, resilient storage are high in the old-fashioned world of data retention. In addition to traditional storage systems, the scale of hyperconverged infrastructure is growing at an alarming rate. Then where Ceph comes in, a free and open-source distributed storage platform with unique design choices that allow it to tackle these challenges.

Ceph is a flexible solution that provides unified, addressable storage of objects and blocks, similar to most cloud providers. It can integrate relatively easily into existing infrastructure. Its capability to scale out on commodity hardware is a boon for organizations looking forward to what the future has in store regarding storage.

What is Ceph?

Ceph is a software-defined storage platform that delivers objects, blocks, and files in one unified system. It is a robust, distributed storage system that can scale out in response to growing data needs with high performance that can grow with an organization's needs. Ceph is well-suited to large-scale storage problems associated with managing vast collections of data (objects) distributed across multiple servers/nodes and needs high-capacity and resilient archiving in the face of hardware failures.

The Architecture of Ceph

At its core, Ceph utilizes a distributed object store (which abstracts storage hardware and allows for the co-mounting of multiple block devices via RADOS) to provide applications with unified access across different types of replicated solutions.

Ceph's architecture can be broken down into several key components:

• Ceph Monitors (MONs): The Ceph Monitors maintain the cluster map and manage the health monitoring in the cluster. They bookend the cluster to keep it consistent, coordinating with other components as necessary so that changes (like adding or removing nodes) are managed correctly.
• Ceph OSDs (Object Storage Daemons): Ceph storage devices for storing data on some nodes in the cluster. Each OSD is responsible for data placement, replication, recovery, etc., which will communicate with other services to guarantee consistent and efficient data distribution across the cluster.
• Ceph Managers (MGRs): These offer different monitoring and node management functions, like collecting cluster performance metrics around the overall state or powering the RESTful API for user interactions.
• Ceph Metadata Servers (MDS): MDS has continued to manage the filesystem metadata, including directory hierarchy and file attributes for CephFile-based storage. Ceph can handle supporting POSIX-compliant file systems like CephFS by using MDSs.
• Ceph Clients: These represent the interfaces through which users and applications can communicate with the Ceph cluster. Ceph provides multiple client types (like Ceph block storage RBD, object storage S3, and Swift via RADOS Gateway, and various file system clients).

Ceph Storage Models

Ceph storage is a solution that supports block, object, and file system storage. These models target different use cases, making ceph storage a flexible storage platform for various workloads.

• Ceph Block Storage (RBD): Ceph block storage service called RADOS block device (RBD) allows you to create Linux host mountable block devices. RBD is well suited for applications that benefit from high-performance random reads and writes, such as virtual machine disk images, databases, or any other application requiring a unified image format, which we expose to them through the block device interface. It provides powerful storage features, which include thin provisioning, snapshots, and cloning, which are part of CEPH's RBD option.
• Ceph Object Storage (RADOS Gateway): RGW (RADOS Gateway) provides the object storage interface for Ceph, allowing applications to access Ceph using standard S3 or Swift APIs. This makes Ceph ideal for applications requiring scalable object storage, such as cloud-native apps (CNAs), large-scale analytics brooks, and distributed content delivery networks within the edge. RGW can also do multi-tenancy, quotas, and bucket versioning.
• Ceph File System (CephFS): A POSIX-compliant filesystem that uses a CEPH cluster. Its distributed file system can be mounted on Linux hosts, suitable for use cases like high-performance computing (HPC), big data analytics, shared file storage, etc. This scalability and fault tolerance ensure that Ceph can handle the data storage volumes.

Scalability and Fault Tolerance

Ceph's greatest strength is its ability to scale. Ceph can scale out by adding more nodes to the cluster (and, therefore, storage capacity and performance). This scale out is realized through Ceph's distributed architecture, to which data can be loaded dynamically and evenly onto every node in the cluster.

This also highlights fault tolerance, another prominent feature differentiating Ceph from traditional storage systems. In a Ceph cluster, data is stored as independent objects, and it gets replicated to multiple OSDs so that if we lose one or more of them, there won't be any issues with accessibility. Ceph can also leverage erasure coding (a space-efficient replacement for replication) to protect data from hardware failure.

Another critical factor in fault tolerance is the Ceph cluster's self-healing capability. If an OSD fails, Ceph moves the data stored on that failed OSD onto other healthy nodes in the cluster so that it still provides a set of raided availability. This self-healing process takes place without human intervention and promptly saves the cluster from failures.

Challenges and Considerations

Ceph has several attractive features, but it is not without its restrictions. Setting up and managing a Ceph cluster is not straightforward, especially for organizations new to distributed storage systems. Proper planning and expertise are necessary to configure the cluster properly so that it performs as the organization desires.

Performance tuning is also a factor in setting up Ceph. For performance, we will need to tune several details, such as the number of OSDs, journal size for each OSD, network configuration, etc. If the performance differs from what is expected, organizations must invest time and resources in understanding Ceph deployment to tune it correctly.

Conclusion

Ceph is a scalable and flexible storage system that provides object, block, and file storage using a common platform. Its scalable architecture, durability, and support for multiple storage models make it a good fit for applications from cloud infrastructure through big data analytics. For organizations seeking to create a robust and future-proof storage infrastructure, the scalability and cost-effectiveness of Ceph are compelling despite its potential complexity in deployment and management. As data grows larger and more intricate, the future of storage is in a number one position on Ceph.